Superhydrophobicity is a surface wettability state in which a solid surface exhibits an extremely high water contact angle, conventionally above approximately 150 degrees, and very low contact-angle hysteresis, so that water droplets rest on the surface in an almost spherical shape and roll off readily while carrying away adhered particles ^[1]. The state arises from the combination of a low-surface-energy chemistry and a hierarchical micro- and nanoscale roughness: air is trapped beneath the droplet, so that the liquid contacts only the uppermost asperities rather than the full solid area, a condition described by the Cassie–Baxter wetting regime ^[2]. Because the roughness amplifies the intrinsic hydrophobicity of the coating material, even a moderately hydrophobic solid can become superhydrophobic when suitably textured, as first demonstrated for the hierarchical wax crystals of biological leaf surfaces ^[3]. The phenomenon is defined physically as the minimization of solid–liquid contact through combined chemical hydrophobicity and structured roughness, which is distinct from simple chemical water repellency on a smooth surface. The governing quantities are the apparent contact angle, the fraction of projected area actually contacted by the droplet, and the hysteresis between advancing and receding angles ^[3].